JPH10206340A - Hard disk inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inspect presence/absence of projections on the surface of a hard disk in a short time by providing a measurement block arranged in an afloat condition on the hard disk as it is turned, an arm which is fixed to a tip thereof and moved in the radial direction of the hard disk, and a sensor to detect the vibration of the measurement block. SOLUTION: A measurement block 102 is moved in the radial direction of a hard disk 10 by tuning a support arm 103 while the hard disk 10 is turned, and during that time, the vibration of the measurement block 102 is detected by a laser Doppler vibration meter, or the vibration propagating the support arm 103 is detected by a contact microphone 30. Presence/absence of small projections on the whole surface is detected within several seconds per hard disk 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard disk inspection apparatus for inspecting the surface of a hard disk for protrusions.

[0002]

2. Description of the Related Art Hard disks have been widely used as storage devices and the like in computer systems, and their capacities have been increasing in recent years. As a part of the increase in capacity, an MR head using a magnetoresistive element whose resistance value changes according to a magnetic field as a head for writing data to a hard disk and reading data from a hard disk has attracted attention. When this MR head is used, high-density recording on a hard disk can be realized, and the capacity of a hard disk can be further increased, as compared with the case where a conventionally used head is used.

[0003] In the case of using not only the MR head but also a conventionally used head, when the disk-shaped hard disk rotates, the head is floated slightly away from the surface of the hard disk due to the action of the air flow. In this state, data is written to the hard disk and data is read from the hard disk (referred to as access to the hard disk). In the case of the MR head, a conventional head is used to perform high-density recording. The weight, shape, and the like of the head are adjusted so as to be closer to the surface of the hard disk, that is, so that the distance between the head and the hard disk surface is, for example, 50 nm to 150 nm.

On the other hand, on the surface of the hard disk, projections having a size of about 1 μm × 1 μm and a height of several tens nm to several hundreds nm may be generated in the manufacturing process. When a large projection occurs, only 50 nm to 100 nm from the hard disk surface
In a floating state, it may interfere with the MR head accessing the hard disk. However, the MR head is extremely sensitive to heat, and an access error may occur even by slight heat generation due to interference with minute projections on the hard disk surface. Therefore, in order to achieve high-density recording and large capacity by employing an MR head, it is necessary to detect the presence or absence of minute protrusions on the surface of a hard disk accurately and in a short time in order to perform an efficient inspection. It is attracting attention as a very important issue.

[0005]

As one of the methods for detecting minute projections on the surface of a hard disk as described above,
A method of actually accessing the hard disk using an MR head is conceivable. However, this method requires a great deal of time to access the entire area of the hard disk. On the other hand, in the final inspection step of the hard disk manufacturing process, it is required that inspection be performed in a few seconds per hard disk. Then, such an inspection in a short time is impossible.

As a method of directly detecting minute projections on the surface of a hard disk, for example, a method of irradiating a laser beam to the surface of the hard disk and detecting irregularities on the surface of the hard disk by using the principle of interference can be considered. The height of the micro projections on the hard disk surface is several tens nm to several hundreds n
Since this is about m, detection with sufficiently high accuracy is possible by this method. However, the size of the surface of the fine projections on the hard disk surface is about 1 μm × 1 μm, and therefore, it is necessary to use an extremely narrowly focused laser beam to scan the entire hard disk surface with such a narrowly focused laser beam. An extremely large inspection time is required for each hard disk.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a hard disk inspection apparatus capable of inspecting the presence or absence of a projection on a hard disk surface in a short time.

[0008]

According to the present invention, there is provided a hard disk inspection apparatus for inspecting the surface of a hard disk for the presence of protrusions. A measurement block that is placed in a floating state on the hard disk by performing the measurement, an arm that fixes the measurement block to the tip and moves the measurement block in the radial direction of the hard disk, and a sensor that detects vibration of the measurement block. It is characterized by having.

Here, the measurement block may use a head for accessing a hard disk. In the hard disk inspection device of the present invention, the sensor may be any sensor as long as it can detect the vibration of the measurement block. And a contact microphone that detects the vibration transmitted through the arm can be suitably used.

[0010] The hard disk inspection apparatus of the present invention includes, for example, a measurement block in which a head for accessing a hard disk is diverted as it is or configured similarly.
Using a hard disk in the same manner as a head that actually accesses, the vibration generated by the measurement block colliding with a protrusion on the surface of the hard disk is detected by using a sensor such as a laser Doppler vibrometer or a contact microphone. As a measurement block, for example, 1 mm x
It is possible to use a measurement block that is extremely large as compared with the size of the protrusion on the hard disk surface (for example, 1 μm × 1 μm), such as a size of about 1 mm, and it is possible to inspect a large area of the hard disk surface at a time.
For example, the entire surface of the hard disk can be scanned in a short time of about several seconds. In addition, the detection accuracy is extremely high as shown in the experimental data described later.

[0011]

Embodiments of the present invention will be described below. FIG. 1 is a schematic perspective view showing a part of a hard disk inspection device according to the present invention. A hard disk 10 to be inspected is attached to a spindle 101 and rotates horizontally in the direction of arrow A. On the hard disk 10, a measurement block 102 is arranged so as to slightly float from the hard disk 10 due to the action of the airflow accompanying the rotation of the hard disk 10.

This measuring block 102 is
The support arm 103 is rotated about the rear end as an axis, and
Is moved in the radial direction of the hard disk 103. In this measurement block 102, the MR head for hard disk access is diverted as it is.

Here, if there is a minute projection on the surface of the hard disk 10, the minute projection interferes with the measuring head 102, and the measuring head 102 vibrates. Therefore, here, in order to detect the vibration of the measuring head, a laser beam 21 of a laser Doppler vibrometer described later is applied to the measuring head.
Is irradiated, or the rear end 10 of the support arm 103
At 3b (preferably the center of rotation), a contact microphone 30 for detecting vibration generated in the measuring head 102 by the interference between the measuring head 102 and the minute projection and transmitted to the support arm 103 is fixed.

FIG. 1 shows both the laser beam 21 emitted from a laser Doppler vibrometer (not shown in FIG. 1) and the contact microphone 30, but both the laser Doppler vibrometer and the contact microphone are connected. It is not necessary to provide, and only one of them may be provided to detect the vibration. FIG. 2 is a diagram illustrating the principle of the laser Doppler vibrometer.

A laser beam having a wavelength λ and a frequency f ₀ is transmitted at a speed V
Irradiates the moving target 1 with. At this time, the reflected laser light reflected by the target 1 undergoes a frequency shift due to the movement of the target 1. Assuming that the angle between the irradiation direction and the reflection direction of the laser light and the moving direction of the target 1 is θ, the frequency transition amount f _D is f _D = 2 · V · cos θ / λ (1). That is, the frequency of the reflected laser light is f ₀ + f _D
Becomes

Therefore, the reflected laser light (frequency f ₀ +
f _D ) and the reference laser light (frequency f ₀ ) separated from the incident laser light and received, a beat signal corresponding to the frequency difference (f ₀ + f _D −f ₀ = f _D ) of the difference is received. Obtainable. The frequency f _D of the beat signal, the target 1, the irradiation direction of the laser beam speed Vco
sθ can be detected. Normally, the reference laser light is not used at the frequency f ₀ , but is used as a frequency-shifted reference laser light (frequency f ₀ + f _M ). Thus, when the target 1 is stationary, a beat signal of the frequency f _M is observed, and when the target 1 moves, the moving direction of the target 1 (moving direction along the optical axis of the irradiation laser light) is positive. The frequency of the beat signal changes from the frequency f _M to the plus side or the minus side in accordance with the minus side, whereby the moving direction and the moving direction of the target can be known.

FIG. 3 is a basic configuration diagram of the laser Doppler vibrometer. A laser beam 20 having a frequency f ₀ emitted from a laser light source 201 is split into a measurement laser beam 21 and a reference laser beam 22 by a beam splitter 202. The measurement laser beam 21 passes through the beam splitter 203 and is applied to the measurement block 102 shown in FIG. When the measurement block 102 vibrates in the optical axis direction of the measurement laser beam 21,
The laser light reflected by the measurement block 102 undergoes frequency transition.

The frequency f ₀ + f having received the frequency transition
The reflected laser light of _D is reflected by the beam splitter 203, reflected by the mirror 204, transmitted through the beam splitter 205, and reaches the light receiver 206. On the other hand, the reference laser beam 22 reflected by the beam splitter 202 is frequency-modulated by the acousto-optic modulator 207, becomes a reference laser beam of frequency f ₀ + f _M , is reflected by the beam splitter 205, and reaches the light receiver 206.

[0019] In the light receiver 206, a beat signal of a frequency f _M -f _D of the difference between the frequency f ₀ + f _M of the reference laser beam and f ₀ + f _D of the reflected laser beam is observed. The beat signal is input to the vibration detection circuit 208, and the frequency change of the beat signal is converted into a voltage signal, whereby the vibration of the measurement block 102 is detected. FIG. 4 is a schematic configuration diagram of a contact microphone.

The microphone generally includes a diaphragm that vibrates in accordance with the vibration of air and has a configuration for picking up the vibration of the diaphragm. The contact microphone 30 has a closed air chamber 302 in front of the diaphragm 301. And the front surface of the sealed air chamber 302 is applied to the surface of the solid 2 (the rear end 103b of the arm 103 in the case of the hard disk inspection apparatus shown in FIG. 1), and the vibration of the solid 2 (arm 103) is sealed. The vibration is transmitted to the gas inside the air chamber 302, and the vibration of the gas is transmitted to the diaphragm 3.
01. The pickup of the vibration of the diaphragm 301 is the same as that of a normal microphone, and the description is omitted here.

In the hard disk inspection apparatus shown in FIG.
While rotating the hard disk 10, the support arm 10
The measurement block 102 is moved in the radial direction of the hard disk 10 by rotating the 3. During this time, the vibration of the measurement block 102 is detected by the laser Doppler vibrometer, or the vibration transmitted to the support arm 103 by the contact microphone 30 is detected. Is done. In this way, the presence or absence of minute projections is detected on the entire surface of the hard disk within several seconds per hard disk.

FIG. 5 is a signal waveform diagram when the vibration of the measurement block is detected using the laser Doppler vibrometer. FIGS. 5A and 5B show signal waveforms in a state in which minute protrusions do not exist on the surface of the hard disk and in a state in which minute protrusions do exist. Comparing FIG. 5A and FIG. 5B, it can be seen that the presence of the microprojections can be detected with sufficient S / N.

FIG. 6 is a signal waveform diagram when vibration of the rear end of the support arm is detected using a contact microphone. FIGS. 6 (a) and 6 (b) correspond to FIGS.
Similar to (b), it is a signal waveform in the case where there is no fine protrusion on the surface of the hard disk, and in the case where there is a fine protrusion. FIG.
Comparing FIG. 6A with FIG. 6B, it can be seen that the presence of the microprojections can be detected with a sufficient S / N even with the contact microphone.

[0024]

As described above, according to the hard disk inspection apparatus of the present invention, the presence or absence of a projection on the hard disk surface can be detected at high speed and with sufficient accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a part of a hard disk inspection device of the present invention.

FIG. 2 is a diagram illustrating the principle of a laser Doppler vibrometer.

FIG. 3 is a basic configuration diagram of a laser Doppler vibrometer.

FIG. 4 is a schematic configuration diagram of a contact microphone.

FIG. 5 is a signal waveform diagram when vibration of a measurement block is detected using a laser Doppler vibrometer.

FIG. 6 is a signal waveform diagram when vibration of the rear end of the support arm is detected using a contact microphone.

[Explanation of symbols]

 Reference Signs List 1 target 2 solid 10 hard disk 20 laser light 21 measurement laser light 22 reference laser light 30 contact microphone 101 spindle 102 measurement block 103 arm 103a arm tip 103b arm rear end 201 laser light source 202, 203, 205 beam splitter 204 mirror 206 light receiver 207 Acousto-optic modulator 208 Vibration detection circuit 301 Diaphragm 302 Sealed air chamber

Claims (4)

[Claims] 1. A hard disk inspection device for inspecting the presence or absence of protrusions on a hard disk surface, comprising: a hard disk rotation device for rotating the hard disk horizontally; and a measurement block arranged to be floated on the hard disk by rotating the hard disk. A hard disk inspection device comprising: an arm that fixes the measurement block to the tip and moves the measurement block in a radial direction of the hard disk; and a sensor that detects vibration of the measurement block. 2. The hard disk inspection apparatus according to claim 1, wherein the measurement block uses a head for accessing a hard disk. 3. The hard disk inspection apparatus according to claim 1, wherein the sensor is a laser Doppler vibrometer that irradiates the measurement block with laser light from above to detect a vertical vibration of the measurement block. 4. The hard disk inspection apparatus according to claim 1, wherein the sensor is a contact microphone that detects a vibration transmitted via the arm.